Piston structure

ABSTRACT

The piston structure comprises a body having a substantial number of circumferential grooves each receiving a piston ring, the radially outer portions of said rings extending vertically in spaced relation to the piston to comprise, in effect, a substantially continuous cylinder wall-engaging sleeve, thus reducing contact of the piston itself with the cylinder wall, groove engaging portions of the rings spaced from the bottoms of the grooves to receive oil for cushioning the rings and permitting expansion of the piston.

1 July 3, 1973 Primary Examiner-Irwin C. Cohen Attorney.lohn Lezdey eta1.

[57] ABSTRACT The piston structure comprises a body having a substantialnumber of circumferential grooves each receiving a piston ring, theradially outer portions of said rings extending vertically in spacedrelation to the piston to comprise, in effect, a substantiallycontinuous cylinder wall-engaging sleeve, thus reducing contact of thepiston itself with the cylinder wall, groove engaging portions of therings spaced from the bottoms of the grooves to receive oil forcushioning the rings and permitting expansion of the piston.

2 Claims, 3 Drawing Figures 92/219, 277/178 Fl6j 1/02,, F16j 9/2092/216, 219, 208,

United States Patent [191 Fiedler PISTON STRUCTURE [76] Inventor: Max G.Fiedler, 585 Pugh Road,

- Strafford, Pa.

{22] Filed: Sept. 27, 1971 [21] Appl. No.: 184,083

[52] US. [51] Int. [58] Field of Search......................

[56] References Cited UNITEDSTATES PATENTS 1,761,982 6/1930 2,012,9569/1935 Chaffin........................... 2,577,022 12/1951Lieberherr........................ 3,315,881 4/1967 Halpin et a1.FOREIGN PATENTS OR APPLICATIONS 356,943 9/1931 GreatBritain.......1..............

PISTON STRUCTURE BRIEF SUMMARY OF THE INVENTION One of the features ofthe invention is that it eliminates the difficulty involved in theexpansion and contraction of the piston body, thus eliminating pistonslap at low engine speeds and before the engine is thoroughly warmed up.Moreover, the invention reduces the residual heat of the piston so thatthe compression ratio can be increased substantially so as to increasethe thermal efficiency of the engine. The piston body may be made of anysuitable material as further discussed below, with such piston bodyprovided with a series of peripheral grooves with interposed lands. Ineach groove is arranged a split piston ring of T-cross section arrangedwith the shanks of the TS in the respective grooves and with theremaining portions of the rings overlying the lands and extending inclose proximity to each other. These piston rings constitute, in effect,a sleeve extending throughout the greater portion of the length of thepiston and such sleeve is made up of individually radially shiftablerings, thus adjusting perfectly to the wall of the cylinder.

The portions of the rings extending into the grooves are slightly spacedfrom the extremities thereof to receive oil which tends to cushion therings and silence operation of the piston, the latter running veryquietly regardless of temperature and engine speeds. Since successiverings are in contact with each other, perfect sealing occurs between therings and the cylinder wall, and each ring is supported and fixed invertical position by the lands on the piston between the rings.

Preferably but not necessarily, the upper end of the piston is providedwith one or more grooves each of which receives a sealing ring havingits outer surface slightly tapered to decrease in diameter downwardly tobe maintained in snug engagement with the cylinder wall by pressure.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevation of a pistonhaving one side broken away and shown in section to illustrate thearrangement of the rings, a portion of the cylinder being shown insection;

FIG. 2 is a similar view somewhat enlarged particularly to show thetapering of the sealing rings; and

FIG. 3 is a perspective view of one of the piston rings.

DETAILED DESCRIPTION Referring to FIG. 1, the numeral indicates thepiston skirt having a head 12. Outwardly of the head 12, the piston bodyis provided with one or more L-shaped grooves 14 in each of which isarranged a sealing ring 16 of L-shaped cross section. The peripheralsurface of the ring is tapered as at 18 (FIG. 2) to utilize combustionchamber pressures to seal the rings against the cylinder wall indicatedby the numeral 20. Beneath each sealing ring 16 is formed a conventionalland 22 to support the ring thereabove. The use of the sealing rings arepreferred but not essential.

Referring to FIGS. 1 and 2, the piston skirt is provided with asubstantial number of peripheral grooves 24, each of which is adapted toreceive a piston ring 26 of T-shaped cross section with the shank of theT, 28, arranged in the narrower portion of the associated groove 24. Theinner extremity of each ring is spaced as at 30 from the innermostportion of its associated groove 24 to receive oil seeping thereintoduring the operation of the engine.

The outer portion of each ring is widened transversely thereof, that is,longitudinally of the piston, as at 32 and these portions have theirhorizontal surfaces 34 in contiguous relationship in the sense of beingclose to each other. In practice, it is preferred that these surfaces bein sliding contact with each other. Each ring 26 is split as at- 36(FIG. 3) and this split may be square with the ends in normal contactwith each other but free to expand.

Above and below each ring 26 the piston body is pro vided with a land 38and these lands serve to fix the piston rings against vertical movementas will be apparent. Obviously, the upper land 40 for the uppermostpiston ring is partly utilized as one of the lands 22, while thelowermost land 42 is arranged beneath the lowermost ring 26.

OPERATION It will be noted that the rings 26 cooperate with each otherto provide, in effect, a continuous sleeve which extends throughout thegreater portion of the length of the piston. The outer surface of thepiston which contacts with the cylinder wall is thus quite limited sinceeach ring 26 is free to expand and contract independently, thusmaintaining the sealing engagement of the rings with the cylinder wall.Because of the sliding contact of the rings with each other and thesubstantial number of rings employed, the split 36 may be square, andleakage past the piston is substantially negligible. As stated, the useof one or more sealing rings 16 is preferred but not essential.

Research has proved that the weight of the piston is of lessconsideration than heat conductivity, particularly in Diesel typeengines. Such research determined that by reducing the residual heat ofthe piston, the compression ratio can be increased substantially so asto increase the thermo efficiency of the engine. Subsequently theautomobile industry developed an aluminum piston for use in a cast ironengine block, and the principal drawback of the aluminum piston was thatit had greater thermal expansion than a cast iron piston. Also, sincethe running clearance must be matched to maximum load and temperature,the piston would be noisy at lighter loads due to piston slap.

A common solution of this problem has been to provide a separate skirtfor thepiston crown and to connect the skirt and crown through a lowexpansion material. This method cannot be adopted for engines whereinthe piston overruns parts and acts as a valve.

The use of the substantial number of piston rings described aboveovercomes such problem. It also has been found that the present pistoncan be utilized in all types of engines so as to give more effectivesealing of the piston with the cylinder wall. It has been found that bythe use of a sleeve comprising a plurality of split rings, as shown anddescribed, the problem relating to the unequal expansion of the cylinderwall and piston is alleviated.

The novel piston contains split sealing rings of L- shape which aresupported by lands on the piston surface. The sealing rings are taperedso that gas pressure holds them against the cylinder wall. Along thepiston for a substantial portion of its length, and preferably thegreater portion of its length, are arranged the piston rings incontiguous relationship and forming, in effect, a continuous sealingsleeve or skirt.

Among the advantages of the use of the split piston rings as a sleeve orskirt for the piston is that the rings adjust so as to provide forcontinuous sealing upon the initial starting of the engine and adjustupon expansion of the cylinder wall and piston during continuousoperation of the engine. Additionally, the rings provide for continuousadjustment when there is uneveness of the cylinder wall due to wearand/or manufacturing defects. The present piston has the followingadvantages:

1. It is easy to manufacture.

2. It is easy to fasten the rings on the piston.

3. it reduces noise due to hydraulic cushioning behind the series ofpiston rings.

4. It does away with clearance problems due to heat expansion of thepiston and/or cylinder.

5. It reduces the residual heat of the piston, thus permitting thecompression ratio to be increased substantially so as to increase thethermal efficiency of ton structure reciprocable in said cylinder, saidpiston structure comprising a piston body including a head portion and askirt portion, said skirt portion having a plurality of groovesextending circumferentially therearound in spaced relation over a majorportion of said skirt portion, said piston body between and adjacentsaid grooves being of smaller diameter than the internal diameter ofsaid cylinder, at least one L-shaped sealing ring mounted at the upperend of said piston in said head portion, said L-shaped sealing ringhaving an outer periphery being tapered to decrease in diameterdownwardly, a plurality of T-shaped support rings arranged in saidgrooves, each of said support rings having the radially inner portionsubstantially equal to the radially outer portion of said ring, theradially inner portion of each of the support rings projecting into oneof said grooves, the radially outer portion of each support rings havinga cylinder surface in slidable engagement with said cylinder, said ringshaving end surfaces in contiguous relationship with each other, wherebysaid radially outer portions of said rings comprise in effect acontinuous cylinder-engaging sleeve extending substantially throughoutthe greater portion of the length of said piston body.

2. An internal combustion engine according to claim 1 wherein saidradially inner portions of said support rings are spaced from thebottoms of the respective grooves so as to provide oil-receiving spacesto cushion radial movement of said rings to increase the degree ofquietness of the operation of said piston structure.

1. In an internal combustion engine, a cylinder, a piston structurereciprocable in said cylinder, said piston structure comprising a pistonbody including a head portion and a skirt portion, said skirt portionhaving a plurality of grooves extending circumferentially therearound inspaced relation over a major portion of said skirt portion, said pistonbody between and adjacent said grooves being of smaller diameter thanthe internal diameter of said cylinder, at least one L-shaped sealingring mounted at the upper end of said piston in said head portion, saidL-shaped sealing ring having an outer periphery being tapered todecrease in diameter downwardly, a plurality of Tshaped support ringsarranged in said grooves, each of said support rings having the radiallyinner portion substantially equal to the radially outer portion of saidring, the radially inner portion of each of the support rings projectinginto one of said grooves, the radially outer portion of each supportrings having a cylinder surface in slidable engagement with saidcylinder, said rings having end surfaces in contiguous relationship witheach other, whereby said radially outer portions of said rings comprisein effect a continuous cylinderengaging sleeve extending substantiallythroughout the greater portion of the length of said piston body.
 2. Aninternal combustion engine according to claim 1 wherein said radiallyinner portions of said support rings are spaced from the bottoms of therespective grooves so as to provide oil-receiving spaces to cushionradial movement of said rings to increase the degree of quietness of theoperation of said piston structure.